1. Field of the Invention
This invention relates to the use of nonionic cellulose ethers selected from the group consisting of hydroxyethyl, hydroxyethyl methyl, hydroxypropyl methyl and hydroxypropyl cellulose having Brookfield viscosities (2% aqueous solution at 20.degree. C.) of at least 3,000 mPa.s as an additive for joint-sealing and coating compounds based on aqueous dispersions of polymers and copolymers, except for polyacrylates and acrylate copolymers, for improving the spreadability, smoothing behavior and resistance to spray water of uncured surfaces of these compounds.
2. Discussion of Related Art
It is known from Ullmann, Enzyklopadie der technischen Chemie, 4th Edition, pages 208-209 that nonionic cellulose ether derivatives, such as hydroxyethyl cellulose (HEC), hydroxyethyl methyl cellulose (HEMC) and hydroxypropyl methyl cellulose (HPMC), are used in polymeric plasters for improving their water retention capacity, workable period, wet adhesion and thickening and setting behavior. In addition, German Patent 36 19 142 discloses the use of water-soluble cellulose derivatives as auxilaries in the mechanical smoothing of uncured surfaces of paste-like materials, particularly joint-sealing compounds, for example based on polyacrylates.
After application, typical known formulations of joint-sealing and coating compounds are normally smoothed with smoothing water or mixtures of water and wetting agents, for example in accordance with German Patent 36 19 142. The use of smoothing agents enables technically and optically satisfactory connections to be established with adjoining structures and to even out imperfections in the surfaces of these materials. The accumulation of the wetting agents present in the smoothing agent causes reduction of the slip resistance on the surface of the sealant and makes slippage itself a possibility. Under certain conditions, the accumulation of wetting agents results in the emulsification of formulation ingredients at the surface of the compounds. Since this alters the composition of the compound at the surface, the performance properties of the sealants can be adversely affected. The depletion of constituents of the compound at the surface can also have a detrimental effect.